Field
Embodiments of the present disclosure generally relate to an apparatus and method for processing gases and substrates in a semiconductor substrate process chamber.
Description of the Related Art
In the fabrication of semiconductor devices, plasma chambers commonly are used to perform various fabrication processes such as etching, chemical vapor deposition (CVD), and sputtering. Generally, a vacuum pump maintains a very low pressure within the chamber while a mixture of process gases continuously flows into the chamber and an electrical power source excites the gases into a plasma state. The constituents of the process gas mixture are chosen to effect the desired fabrication process
It has been observed that some of conventional plasma processing chamber designs in which the plasma is generated between two parallel electrodes (i.e., capacitive coupling plasma) can cause unwanted particle contamination on a substrate surface due to ion bombardment of the electrodes. In deposition processes that require a higher RF input power (over 550 W), once the plasma has been created, a high self-induced negative DC bias is also naturally established at the powered electrode. The electrical potential difference between the plasma and the self-induced negative DC bias forms a sheath voltage at or near the powered electrode. This sheath voltage causes positive ions within the plasma to accelerate toward the powered electrode, resulting in ion bombardment of the powered electrode. In instances where the powered electrode includes a protective coating layer, a portion of the protective coating layer may flake off as a result of the ion bombardment after a long period of time and contaminate the substrate surface. While a lower RF input power can be used to generate the plasma (and thus reduce particle contamination), the film deposition rate will be decreased, which in turn lowers the process yield.
Therefore, there is a need in the art for an apparatus and process that effectively reduces the generation of contaminating particles on the substrate surface and maintains high process yield.